Derivative Instruments and Hedging Activities - Effect Of Derivatives On Interest Income (Details) - Designated as Hedging Instrument - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivative, net	$ (376)	$ 677
Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivative, net	(335)	711
Interest Income | Fair Value Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivative, net	(41)	(34)
Interest Income | Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivative, net	271	1,856
Interest Expense | Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivative, net	$ (606)	$ (1,145)